"But," Melvin added, "anything can change in this game."
And, with an off-day on the A's schedule Monday and Tyson Ross struggling, Melvin admitted he plans to "tinker with the rotation."
Jarrod Parker, who is scheduled to start on Tuesday against Toronto, has already joined the rotation and there is speculation Brad Peacock, acquired from the Nationals during the offseason in the Gio Gonzalez trade, could be the next starter to be called up.
Following Friday night's 7-2 shellacking, in which Ross lasted just 3 1/3 innings, his briefest stint of the year, allowed seven runs on nine hits, and was called for a balk with two runners on base, Melvin said he hadn't thought about Ross' future status.
"I thought it all revolved around his fastball. It looked like [Kurt Suzuki] had a tough time corralling it," Melvin said. "When he was calling some pitches, they weren't getting there. When he [Suzuki] was calling away, he [Ross] was missing sometimes inside."
In his last two starts, covering just 7 1/3 innings, Ross has been ripped for 20 hits and 16 earned runs. He admitted he has work to do in order to improve before he makes his next start.
"I have to work on keeping the ball down in the zone and focus on getting the first pitch over for a strike," said Ross, the first A's starter since Ben Sheets in 2010 to allow seven or more runs in back-to-back starts.
"I need to do a better job of getting ahead of the hitters," he said. "My whole game plan out there is to get ahead, get a nice ground ball for the defense."